This invention relates to communications systems and more specifically to an integrated digital multi-channel communications system for operation with multiple mobile units, dispatch agencies, communications channels, and methods.
Mobile communications systems are used in many applications such as police and fire department dispatching and now in such new applications as control of transit bus systems and other municipal government functions. These new communications requirements are leading to the development of integrated local government communications systems.
Conventional communications systems in use in such applications as local governments include mobile users and dispatch agencies that operate on a small number of channels, sometimes as few one or two, with one or two tower sites usually over voice channels only while some systems are now offering data communications. Mobile users communicate with their dispatch agencies over these channels using their system tower sites. Automatic routing of messages between users is not available in these conventional communications systems. If the loading on channels becomes excessive, users are asked to move to alternate channels and if the range from a mobile unit to the tower site becomes excessive, the users must manually switch over to another tower site if available.
The new applications of communications to such requirements as integrated local government systems have increased the need to support large fleets of 4000 vehicles or more over large geographical areas. With the increase in the number of mobile and dispatch agency users, the need to effectively increase the capacity of the communications system by utilizing more channels has arisen. When channel capacity has reached overload conditions, mobile units must be handed off to other channels to balance the channel loading. When mobile units exceed the range of fixed station or tower sites, the mobile unit must be handed off to another tower site with the needed coverage. These hand-offs must be done automatically without loss of messages and be transparent to the users.
The predominant form of communications with most previous communications systems is voice. Voice communications are slow and require a voice channel for each user. The number of voice communications channels must be reduced while increasing the rate of information transfer. To do this digital communications methods must be developed that enable rapid transfer of data over a limited number of channels.
Currently local government agencies have a large variety of existing communications systems that must be supported due to the high cost of replacing these systems. The mobile units must also interface alternate forms of communications such as cellular phone systems. In addition a multiple local government agencies require communications through a single common communications system to reduce infrastructure costs.
Integrated local government communications systems require reliable operation for the safety of the system users and the public being served. The communications system must be reliable and provide failsafe capabilities.
Accordingly a new multi-channel communications system is needed to meet the current and future needs of users in such applications as integrated local governments.
The objectives of the invention are met with a new mobile digital multi-channel communications system architecture that has features in the mobile units, tower sites, dispatch agencies, and a multi-channel controller (MCC) to arrive at a cohesive integrated communications solution.
The multi-channel communication system includes multiple mobile units, several tower sites, a multi-channel controller, and several dispatch agencies. In some applications redundant multi-channel controllers may be used to improve system reliability. The communications system is primarily designed to be a time division multiple access (TDMA) system with interface capabilities to wide variety of existing systems. The multi-channel communications system includes mobile units each equipped with a vehicle logic unit (VLU) for control of the mobile unit and its interface with the system. The mobile units have a form of identification used in establishing communications. Also included are tower sites for one or more TDMA communications channels for communications with the mobile units. Several dispatch agencies also having a form of identification for use by the dispatch agencies to define the mobile units for which the agencies are responsible are connected to the communications system. The multi-channel controller is a computer running the multi-channel communications software to control the multi-channel communications system. A multi-channel controller is connected to the tower sites and the dispatch agencies for directing outgoing messages from the dispatch agencies to the mobile units and for routing incoming messages from the mobile units to dispatch agencies according to the form of identification. The multi-channel controller determines TDMA channel loading and hands off selected mobile units from one channel to another when loading on a channel becomes excessive. The multi-channel controller also selects and connects the mobile units to another tower site in another geographic area when the geographic area covered by the first tower site becomes inadequate. The multi-channel controller routes messages to a new TDMA channel when a current channel of communications fails.
It is therefore an object of the present invention to provide a new multi-channel communications system to meet the current and future needs of users in such applications as integrated local governments.
It is another object of the present invention to provide a communications system that increases the data network capacity through the use of additional channels to increase the bandwidth or load capacity automatically as the need arises.
It is a feature of the present invention to route messages from the mobile units to the proper dispatch agencies and from the dispatch agencies to the proper mobile units without being constrained to any individual channel or tower site by using forms of identification with the mobile units and the dispatch agencies.
It is another feature of the present invention to determine communications channel loading to hand off the mobile units from one communications channel to another communications channel at a tower site when loading on the first communications channel becomes excessive.
It is a feature of the present invention to increase the geographic coverage of the communications system through the use of multiple tower sites to enable the mobile units to roam between coverage areas of the tower sites while maintaining communications by selecting a new tower site when the coverage of the first tower site is exceeded.
It is an advantage of the invention to interface many types of existing communications systems.
An advantage of the invention is a reliable communications system with redundant and fail safe functions at a low cost to the system users.
These and other objects, features, and advantages are disclosed and claimed in the specification, figures, and claims of the present application.